1. GSM Vs. CDMA An Overview Bhushan G. Jagyasi
Lecturer, Elex & Tele Comm Dept.
Thadomal Shahani Engineering College

2. Classification Of Existing Systems
Technologies
TDMA/FDMA
CDMA
GSM (European Standard)
IS 136 (U.S Standard)
PDC (Japnese Standard)
IS 95 (U.S Standard)

3. Evolution Chart Broad Band 4G Service type Narrow Band Wide Band
1G G G
Multimedia
Wireless Internet Mobile system
Digital
IS 95
IS 136
GSM
IMT 2000
Voice
Analog
AMPS
~ 24kbps ~64kbps ~2Mbps ~20Mbps
Years

4. Access technology
PN Code
Freq
Freq
Freq
Time
Time
Time
FDMA
TDMA
CDMA

5. Comparison BetweenTechnologies
Digital Mobile technology
User’s Dec-02
User’s Dec-03
Growth in2003
% Growth
Share Of Growth
CDMA
145.2
181.0
35.4
24.3%
15.6%
GSM
790.5
970.8
180.3
22.8%
79.5%
PDC
60.1
63.1
3.0
5.0%
1.3%
TDMA
107.4
113.0
5.5
5.1%
2.4%
3 GSM
(W CDMA)
0.2
2.8
2.6
1708.5%
1.2%
GLOBAL USER BASE
1103.7
1330.6
226.9
20.69%
100%

6. GSM
An Overview

7. GSM The European TDMA Digital Cellular Standard
Services Provided By GSM
1. Telephony
- Basic Teleservice
2. Other Services
-Emergency calling
-Voice Messaging

8. GSM The European TDMA Digital Cellular Standard
Services Provided By GSM (Cont..)
3. Bearer Services
- Low Speed data transfer (upto 9.6 Kbps)
-Group 3 Fax and Sms
4. Suplementary Services
- call offering , call forwarding, call restriction,
call waiting, call hold.
- Multiparty teleconferencing, special schemes

9. GSM The European TDMA Digital Cellular Standard
General Architecture Of GSM
HLR
VLR
BSC
BTS
PSTN,
ISDN
MSC
SIM
BTS
BSC ME
EIR
AuC
Abis Um A MS
BSS NS
Mobile station
Base Station Subsystem
Network
Subsystem

10. GSM The European TDMA Digital Cellular Standard
Mobile Station (MS): Two Blocks
Mobile Equipment (ME)
Subscribers Identity Module (SIM)
Function of Mobile Station:
1. Personal Mobility

11. GSM The European TDMA Digital Cellular Standard
Function of Mobile Station:
1. Personal Mobility
SIM
SIM
SIM
SIM
SIM
SIM
SIM

12. GSM The European TDMA Digital Cellular Standard
Mobile Station (MS): Two Blocks
Mobile Equipment (ME)
Subscribers Identity Module (SIM)
Function of Mobile Station:
1. Personal Mobility
2. IMEI (International Mobile Equipment Identity)
3. IMSI (International Mobile Subscriber Identity)

13. GSM The European TDMA Digital Cellular Standard
Base Station Subsystem (BSS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)
BSC

14. GSM The European TDMA Digital Cellular Standard
BSC: Base station Controller
1. It manages radio resources for one or more BTS.
2. Allocation and Deallocation of channels.
3. Transmitter power control.
4. Handoff control
BTS : Base Tranceiver station
1. It defines the cell .
2. It handles the radio link protocol with the mobile station
BSC

15. GSM The European TDMA Digital Cellular Standard
HLR
VLR
PSTN,
ISDN
BSC
MSC
EIR
AuC
Network Subsystem
MSC: Mobile Switching Center
HLR: Home Location Register
VLR: Visitor Location register
AuC: Authentication Center
EIR: Equipment Identity Register

16. GSM The European TDMA Digital Cellular Standard
Mobile Switching center:(MSC)
call set up/supervision/release
call routing
billing information colllection
mobility management
paging, alerting, echo cancellation
connection to BSC, other MSC and other local exchange networks
Access to HLR and VLR

17. GSM The European TDMA Digital Cellular Standard
Home Location Register (HLR)
One HLR per GSM operator
Contains permanent database of all the subscribers in the network
contains MSRN(mobile station routing no.)
It is reffered for every incomming call

18. GSM The European TDMA Digital Cellular Standard
Visitor Location Register(VLR)
Temporary visitors database
One VLR per MSC
Authentication Center(AuC)
Provides security
Authentication and encryption
Equipment Identity Register:
Contains IMEI

19. GSM The European TDMA Digital Cellular Standard
Location Update
VLR
BSC
MSC
HLR
GMSC
BSC
MSC
PSTN.
ISDN
VLR

20. GSM The European TDMA Digital Cellular Standard
Mobile call originating
VLR
BSC
MSC
HLR
GMSC
BSC
MSC
PSTN.
ISDN
VLR

21. GSM The European TDMA Digital Cellular Standard
Mobile call terminating
VLR
BSC
MSC
HLR
GMSC
BSC
MSC
PSTN.
ISDN
VLR

22. GSM The European TDMA Digital Cellular Standard
Handoff
GMSC
Handoff is of
3 types
1. Intra BSC
2 Inter BSC
3. Inter MSC
MSC
MSC
BSC
BSC
BSC

23. GSM The European TDMA Digital Cellular Standard
GSM Radio Aspects :
Uplink(Mobile to base)
MHz (Total 25 MHz)
Downlink ( Base to Mobile)
MHz (Total 25 MHz)
Total 45 MHz spacing for duplex operation
GSM uses TDMA and FDMA

24. GSM The European TDMA Digital Cellular Standard
GSM Using FDMA
200KHz
890MHz Mhz
Uplink Freq
Total Frequency range(Uplink)=25Mhz
Spacing between two carriers= 200kHz
No. of Carriers=25MHz/200KHz = 124

25. GSM The European TDMA Digital Cellular Standard
GSM Using TDMA
TDMA Frame is divided into 8 time slots.
Freq
Time slots
Down Link carrier 1 2 3 4 5 6 7
200 KHz
45MHz
Up Link carrier
0 3 1 3 2 3 4 5 5 6 7
4.6 ms
0.57ms
Time

26. GSM The European TDMA Digital Cellular Standard
Classification of channels in GSM
Two types
Traffic channels (TCH)
Control channels (CCH)
Channels are used to carry speech , data and control information.
Traffic Channels are defined using 26 TDMA frame multiframe.

27. GSM The European TDMA Digital Cellular Standard
Length of 26 TDMA frames = 120 msec
Length of 1 TDMA frame =120/26
= msec
1 TDMA frame consists of 8 burst frames
Length of 1 burst frame = 0.577msec
Out of 26 frames 
24 are TCH used for traffic
1 is SACCH used for control
1 is unused

28. GSM The European TDMA Digital Cellular Standard
Frame Multiframe
Duration=120ms 1 2 10 24 25
Tdma Frame
Duration=4.615ms 1 2 3 4 5 6 7
Format of a single Burst
Duration=0.577ms 3 57 1 26 57 25
Data
Training
Data

29. GSM The European TDMA Digital Cellular Standard
Speech coding
Speech is digitized by PCM, o/p of PCM is 64Kb/s
It is further reduced by Regular pulse excited-Linear predictive coder, bit rate achieved 13kb/s for full rate (260 bits in 20 msec)
Further encoded for error correction, 456 bits per 20 msec, bit rate = 22.8 Kb/s
456 bits are divided into 8 blocks and transmitted during 8 burst periods.

30. GSM The European TDMA Digital Cellular Standard
Classification of Channels
1 Traffic (TCH)
Speech
Full rate 22.8 kb/s
Half rate 11.4 kb/s
Data
9.6kb/s
4.8kb/s
2.4kb/s

31. GSM The European TDMA Digital Cellular Standard
2 Control (CCH)
Broadcast (BCCH)
Freq correction (FCCH)
Synchronization (SCH)
Common (CCH)
Paging (PCH)
Access grant (AGCH)
Random Access (RACH)
Dedicated (DCCH)
Fast Associative (FACCH)
Slow Associative (SACCH)
Stand alone (SDCCH)

32. GSM The European TDMA Digital Cellular Standard
GSM Security MS
NETWORK
Random no Ki Ki Ki Ki A3 A8 A3 A8
SRES Kc Kc
Equal
SRES

33. Code Division Multiple Access (CDMA) An Overview

34. CDMA Classification of CDMA Systems CDMA SYSTEMS CDMA one CDMA 2000
Wide Band
IS95
IS95B
JSTD 008
Narrow Band

35. CDMA Multiple Access in CDMA: Each user is assigned a unique PN code.
Each user transmits its information by spreading with unique code.
Direct Sequence spread spectrum is used.
Users are seperated by code not by time slot and freq slot.

36. CDMA Concept of CDMA Users share same bandwidth User axis shows
cumulative signal strength
of all users
User
Code 4
Code 3
Code2
Code 1
Freq

37. CDMA Spread Spectrum and Multiple Access: Spread Spectrum
In Spread spectrum data is transmitted with BW in excess to minimum BW necessary to send it.
Spread spectrum is achieved by spreading with PN code at transmitter . Same code is used to despread the received signal at reciever
How do we get increased spectrum
Wide band
code seq
Narrow band
inputsignal
Wide band
Spreaded seq X

38. CDMA Advantages of spread spectrum: Multipath Rejection
Immunity to interference and jamming
Multiple access
Code 1
Code2
Code 3
Code 4
Freq
User

39. CDMA Comparison between CDMA and TDMA/FDMA:
In TDMA Band width available for transmission is small which leads to compromise in quality of transmission. Whereas in CDMA systems entire spectrum is used which enhances voice quality.
In TDMA/FDMA, cell design requires more frequency planning which is tough job. Whereas in CDMA frequency planning is minimal.
TDMA is Band limited system. CDMA is Power limited system

40. CDMA Types of Codes used in CDMA: Walsh code Short PN code(16 bit)
Orthogonal codes
In IS 95A and IS 95B 64 Walsh codes are used
In CDMA Walsh codes are used
Short PN code(16 bit)
Used to identify the BS and hence the cell
Long PN code(42 bit code)
Used to identify mobile station on reverse link

41. CDMA Formation of channels (IS 95)
PN Code( Chip code) has rate of 1.23 MHz
Chip rate = 1.23 MHz (spread BW)

42. CDMA Forward Link (BS to MS) Forward CDMA Channels PILOT SYNC PAGE
TRAFFIC
TRAFFIC W0
W32 W1 W7 W9 W0
TRAFFIC
DATA
POWER
CNTRL
SUB CH

43. CDMA Reverse Link Channel (BS to MS)
Here CDMA ch does not follow strictly orthogonal rule.
It consists of 242 logical channels. 42 bit long PN code is used to distinguish between channels.
Reverse CDMA Channels
Access
Ch 1
Access
Ch n
Traffic
Ch 1
Traffic
Ch m
m mobiles tryin to gain access to system
m mobiles engaged in calls

44. CDMA Other key Factors Diversity Power Control
Time diversity
Frequency diversity
Space(Path) diversity
Power Control
Handoff: It supports Soft Handoff

45. CDMA
Soft Handoff
Signal strength
Distance

46. Thanks